This invention relates to filling tubes for automatic container filling machines of the type that are widely used in the beverage industry for filling containers such as bottles and the like.
Automatic container filling machines involve a series of dispensing heads and conveyor mechanisms which automatically operate to bring the beverage containers to be filled, such as glass bottles, into contact and seated with the heads, whereupon a liquid, such as beer, is automatically discharged into the containers.
The filling cycle includes the initial step or stage of placing the bottle or other container in sealed relation with a filling head which includes a filling tube, usually made of stainless steel, which is vertically disposed to project downwardly into the container being filled. A container centering bell is mounted to be vertically slidable upon the filling tube. As the container is placed into position to be filled with liquid, the mouth of the container is seated against a sealing ring in the centering bell when the centering bell is in its lowered position. The container is then raised and the centering bell slides up the filling tube until the filling tube is in position, projecting downwardly into the container. The container may then be placed in communication with a gas reservoir so that pressure is established in the container, prior to filling the container with beer or other liquid. When the container is filled to a predetermined level with liquid, the flow is stopped, and the container is lowered from the filling apparatus.
The outer diameter of the filling tube is usually large so that it fits within the mouth of the container with a relatively small clearance. As a result, the hard stainless steel tube may contact the glass container when the tube is inserted into the neck of the bottle, usually causing chipping of the glass which can enter the container and contaminate the product. The hard stainless steel filling tube can also cause damage to the slidable sealing bell which fits over the top of the container, and which is conventionally made from brass or a similar material. The damage to the sealing bell is caused by a stop means formed at the lower end tip of the tube which prevents the bell from sliding beyond the end of the tube. When the container is lowered from the filling head and the bell slides down the tube, the stop on the tip of the hard stainless steel tube hits the softer brass bell. The continual dropping of the bell onto the stop on the tube during the operation of the filling machine can eventually damage the bell.
It would be advantageous to replace the tubes of stainless steel with those of another material, but stainless steel tubes are preferred because of their strength, durability and cleanliness. The end tip of the stainless steel tube could be made of a material other than stainless steel, but there are many problems associated with such a design. One problem relates to the formation of an effective seal between the tip and the stainless steel tube body. Without an effective seal, pockets could form between the tip and the tube body, providing a reservoir for the product to stagnate and for bacteria to collect. Another problem relates to the absorbency of the material of the tip. The tip must be soft, but many soft materials also tend to swell when wet, causing the tip to expand and loosen from the tube body.